Cordless power tools provide many advantages over traditional corded power tools. In particular, cordless tools provide unmatched convenience and portability. An operator can use a cordless power tool anywhere and anytime, regardless of the availability of a power supply. In addition, cordless power tools provide increased safety and reliability because there is no cumbersome cord to maneuver around while working on the job, and no risk of accidently cutting a cord in a hazardous work area.
However, conventional cordless power tools still have their disadvantages. Typically, cordless power tools provide far less power as compared to their corded counterparts. Today, operators desire power tools that provide the same benefits of convenience and portability, while also providing similar performance as corded power tools.
In cordless power tools operated via a battery pack, proper management of the temperature of the battery pack is important. While high battery temperature may damage the cells and presents a fire hazard, low battery temperature increases the impedance of the battery cells. Such a condition causes the voltage of the cells to sag well below their nominal voltage. What is needed is a mechanism that protects the battery pack in cold temperature conditions.